Rock drill



W. A. SMITH.

ROCK DRILL.

APPLICATION FILED AuG.13. 1920.

Patented Oct. 3, 11922.

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WILLIILM it. SMITH, O31" PHILLIPSBURG, NEW JERSEY, ASSIGNOR T0 INGERSOLL-RANU COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

RUSK DRILL.

Application filed August 13, 1920. Serial' No, 403,355.

T 0 all who-m it may concern:

Be it known that 1, WILLIAM A. SMITH, a citizen of the United States, a resident of Phillipsburg, county of Warren, State of New Jersey, have invented certain new and useful Improvements in Rock Drills, of which the following is a. specification.

This invention relates to fluid operated rock drills of the hammer type, but more particularly to such a machine having a differential piston formel with a single head and a forwardly extending reduced shank. Live fluid pressure is constantly supplied to the forward end or rearwardly driving pressure surface of the piston for constant pressure return of the piston on the back stroke and pressure is intermittently supplied to and exhausted from the rear end or forwardly driving pressure surface of the piston for the forward StIJkG.

This distribution of fluid pressure is ultimately controlled by the piston itself, but in order to produce a late admission against the rear surface of the piston on the rearward stroke and a late cut-off on the forward stroke, I provide a valve controlling communication between forward and rearward admission passages leading respectively to a forward admission port and another admission port located rearwardly of the said forward admission port. By this means, I am enabled to produce a longer back travel of the piston and a longer admission of fluid pressure against the rear surface of the piston on the forward stroke.

The valve is of the diflerential type and is actuated by fluid pressure on opposed operative surfaces, but I prefer to subject one operative valve surface to constant pressure tending to return the valve to a position to open communication between said two forward and rearward admission passages, and the other opposed operative surface of the valve is subjected to fluctuating pressure tending to move the valve to close communication between said admission passages' To these ends the invention consists of the apparatus and device shown in the accompanying drawings, in which- Figures 1 and 2 are diagrammatic longitudinal sectional elevations of a rock drill embodying the invention in one of its preferred forms, showing the piston hammer in two different positions.

Referring to the drawings, A represents the cylinder of a rock drill having the front supplied through the admission port K from the inlet L. Ports and passages are provided for intermittently supplying pressure to the rear chamber O of the larger bore Id and this portion of the c linder is provided with the exhaust port The supply of motive fluid in the rear chamber 0 behind the piston D is controlled partly by the valve Q operating in the valve chamber R and in this instance having a. front head. S and a rear head T connected by the reduced neck U. The front head S in this instance has the reduced shank V against the surface W of which pressure is constantly maintained by means of the passage X communicating with the constant pressure chamber of the cylinder. The constant pressure against the smaller pressure surface W of the valve constantly tends to force the valve to its rearward position as indicated. in Figure 1. The other and larger opposed operative pressure surface Y of the valve is subject to an intermittent or fluctuating pressure through the passages Z and a communicating with the intermittent pressure chamber 0 in the cylinder. A forward admission port 6 has a forward admission passage 0 leading to the valve chamber R and a rearward admission port cl has a rearward admission passage 6 also leading to the valve chamber R. The rearward admission port (Z also communicates with the supply passage (1 for the rear end of the cylinder. The valve chamber R as shown is vented to atmosphere at the atmospheric port f in front of the valve head S.

In the operation of the machine, let it be assumed that the piston is at the forward end of its stroke as indicated in Figure 1 and is about to start on the back stroke.

The rear end of the cylinder is shown exhausting through the exhaust port P and pressure is also exhausted from the rearward pressure surface Y of the valve through the passages Z aud o and through the cylinder to the exhaust port P. The constant pressure on the front differential surface W of the valve has caused the valve to throw over or move to its rearward position as indicated in Figure l, closin communication between the forward anr rearward admission passages c and e. As the piston travels back under constant pressure, the exhaust port P is closed, but the shoulder J on the piston overruns the forward admission port Z) without admitting pressure to the rear surface of the piston head D because the forward admission passage 0 is still closed by the valve Q.

After the main head D over-runs the cylinder exhaust port P, the shoulder J on the piston then over-runs the rearward admission port d, which admits pressure past the piston shank or extension E to the rear of the cylinder bore and also through the passage Z to the rear end Y of the valve, WlllCll throws the valve to its forward position as indicated in Figure 2, because of the differential pressure axis of the valve, thus opening communication between the forward and rearward admission passages c and e and supplying full pressure behind the piston head D.

Owing to the fact that no pressure is supplied to the rear of the main cylinder head D when the forward admission port 6 is uncovered by the piston shoulder J, the piston has a substantially long rearward stroke, before the. forward and rearward admission passages c and e are placed in communication by the action of the valve Q, and on the other hand, the piston is given a late cut-off on the forward stroke, because cut-ofi' does not take place when the rearward admission port (1 is over-run by the piston bore J,but is delayed until the forward admission port 7) is over-run by the piston as indicated in Figure 1.

I claim:

In a fluid actuated rock drill of the hammer type, the combination of a cylinder and a differential piston having a head provided with forwardly and rearwardly acting pressure surfaces and a forwardly extending reduced shank, means for maintaining fluctuating pressure tending to open com munication between said forward and rearward admission passages, and the front head having a reduced shank provided with a rearwardly acting pressure surface subject to constant pressure tending to hold the valve in a position to close communication between said forward and rearward admission passages.

In testimony whereof I have signed this specification.

WILLIAM A. SMITH. 

